Drive acting on both sides for adjustment devices

ABSTRACT

The invention relates to a drive acting on both sides for adjustment devices, including a rotationally mounted drive lever for producing a rotational movement that can be selectively effected in one direction of rotation or in the other direction of rotation, a drive wheel that can only be rotated when the drive lever is moved from a zero point position, at least a one-piece coupling element having two coupling areas for transmitting a torque to the drive wheel, in addition to a sliding block guide with areas for controlling the coupling element. The coupling element can be displaced radially and is tiltably mounted in a guide and coupled by both coupling areas in the zero point position of the drive lever to the drive wheel in an elastic manner so that the non-loaded coupling area is uncoupled from the drive wheel by the sliding block guide when the drive lever moves from the zero point position and remains uncoupled when the drive lever moves in the opposite direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of International application numberPCT/DE00/01810, filed May 31, 2000, which in turn claims priority toGerman patent application number 199 27 033.3, filed Jun. 4, 1999.

FIELD OF INVENTION

The invention relates to a drive acting on both sides for adjustmentdevices. The invention is intended in particular for the adjustment ofvehicle seat components such as seat backs and seat cushions.

BACKGROUND OF INVENTION

From DE 195 27 912 A1 a drive acting on both sides is known where adrive lever is mounted on a drive axle and supports swivel couplingelements whose free ends provided with toothed elements can be broughtinto engagement with the teeth mounted around the circumference of adrive wheel. The swivel coupling elements are associated with a slidingblock guide which lifts the relevant unloaded coupling element from thegearing of the drive wheel according to the swivel direction of thedrive lever. Spring areas are thereby provided on both sides and outsideof the sliding block guide to exert on the coupling elements a forcedirected against the engagement direction of the teeth so as to preventany so-called ratchet or rattling noises.

The drawback with the adjustment drive known from DE 195 27 912 A1 is inthe first place the relatively large number of parts. In particular twoindependent coupling elements are required for an adjustment on bothsides; this is linked with a correspondingly large structural spacetaken up by the adjustment drive. Secondly an expensive construction isrequired in order to guide the coupling elements in a defined manner andto prevent the teeth of the coupling elements from catching on the teethof the drive wheel when the drive lever is returned to the zero pointposition.

SUMMARY OF THE INVENTION

Starting from the prior art the object of the invention is to provide adrive acting on both sides which produces a rotary movement, which usesa small number of individual parts, is simple to assemble and ischaracterised by a compact construction. The drive during use shouldoperate substantially free of play and produce no switching or rattlingnoises.

The solution according to the invention proposes that the couplingelement is mounted for both radial displacement and tilting movement ina guide whereby the two coupling areas are coupled spring-elastically tothe drive wheel when the drive lever is in the zero point position. Whenthe drive lever is moved out of the zero point position the non-loadedcoupling area is uncoupled from the drive wheel through the slidingblock guide and remains uncoupled when the drive lever is moved in theopposite direction, thus moved towards the zero point position.

Although play is required owing to the one-piece design of the couplingelement, the drive appears subjectively free of play since the actualidling path which has to be covered up to rotation of the drive wheel isloaded through the spring-elastic pretension. This pretension can beproduced for example by a coil spring which is supported on one sideradially on the drive lever and on the other side on the couplingelement, whereby the coupling area is pressed into the associatedcoupling area of the drive wheel. By way of example a coil springpresses the coupling element against the drive wheel whereby themovement of the drive lever overall is found to be free of play.Furthermore with the solution according to the invention no engagementclick occurs since the coupling element is brought smoothly through theresilient tension into an entrainment position and not merely byapplying a drive force.

In order to ensure a secure accurate guide of the coupling element inthe radial direction a guide element is provided which is connected tothe coupling element and which engages in a recess of the drive lever.This recess thereby extends in the radial direction and is formed forexample as an oblong hole.

In an alternative embodiment the guide element is mounted on the drivelever and the radial recess which acts as a type of slide guide isworked into the coupling element. The guide element can be connected inone assembly process, for example by welding, riveting or screwing, tothe drive lever or to the coupling element or can be formed by pressingor drawing. The recess is normally punched out. Similarly, the formationof the recess is possible in a re-shaping process.

Under certain circumstances it can be favourable in order to guarantee auniform substantially non-jerky movement of the guide element to providea slide block which connects the guide element to the radial recess.Through the slide block it is possible to produce a favourable frictionpairing irrespective of the material of the guide element and of thecomponent part enclosing the recess.

This recess is preferably dimensioned so that with maximum displacementof the coupling element towards the drive axle both coupling areas arenot exactly coupled to the drive wheel. It is thereby reached that theplay of the adjustment drive is minimal.

According to the invention a spring is mounted between a housing of theadjustment drive and the coupling element wherein the spring biases thecoupling element radially in the direction of the drive wheel so thatthe two coupling areas in the zero point position of the drive leverreliably adjoin the drive wheel.

In one embodiment of the invention a spring is provided between thedrive lever and the coupling element whereby it is favourable if thespring is mounted between the drive lever and a guide element of thecoupling element.

In order to ensure a definite engagement of the coupling areas with thedrive wheel it is advantageous to provide a keyed connection to transferthe force applied through the drive lever. To this end both the couplingareas of the coupling element and the circumference of the drive wheelare provided with teeth which are associated with each other so that thetwo toothed areas can engage in each other. The teeth of the drive wheelcan thereby be formed as internal or external teeth.

Since the manufacture of the teeth, particularly internal teeth, istime-consuming and expensive, as an alternative to the keyed connectionthe coupling area is coupled in friction engagement with the drivewheel. The coupling areas of the coupling element and the circumferenceof the drive wheel are thereby designed accordingly, for example bycoating with a friction lining so that the transfer of the requiredtorque between the coupling element and drive wheel takes place throughfriction engagement.

The sliding block guide for controlling the coupling element is formedin one embodiment of the invention in a cover element of the drive.

In one development of the invention resilient elements are provided onboth sides outside of the guide areas of the slide block and duringmovement of the drive lever towards the zero point position cause thecoupling area which was previously loaded, to be lifted from the drivewheel. The spring force is thereby designed so that when the drive leveris moved out of the zero point position it allows the coupling areas toadjoin the drive wheel and at the same time guarantees that the couplingelement is lifted when no force is introduced through the drive leverfor adjusting the seat back for example.

For this, guide elements are arranged on the coupling element in theform of pins for example which are guided in the sliding block guide andwhich are in contact outside of the sliding block guide areas withresilient areas in order to engender the lifting movement of thecoupling element in the absence of drive force so that no rattling orratchet noises occur during the resetting movement. In a furtherdevelopment of the invention the guide elements have a non-roundedcorner section so that during movement of the coupling element over thezero point position the reversing play is minimised.

A further development of the solution according to the invention ischaracterised in that a secondary force is exerted on the couplingelement during an adjustment process such that when the drive lever ismoved out of the zero point position torque is produced on the loadedcoupling area in the direction of the drive wheel and when the drivelever is moved towards the zero point position torque is produced in thedirection of lifting the loaded coupling area away from the drive wheel.

With this development of the solution according to the invention a morecost-effective play-free drive is provided which causes on one side afixed coupling between the coupling area of the coupling element whichis active in the relevant adjusting direction, and the drive wheel whenthe drive lever is moved out from the zero point position and on theother hand ensures a silent resetting of the drive lever back into thezero point position.

An advantageous development of this solution according to the inventionfor a drive where the coupling areas of the coupling element are formedas teeth, and toothing is provided on the circumference of the drivewheel associated with the teeth, is characterised in that when the drivelever is moved out from the zero point position torque is produced onthe loaded coupling area in the sense of a toothed engagement and whenthe drive lever is moved in the direction of the zero point positiontorque is produced in the sense of separating the toothed engagement.

With this design of the invention on the one hand there is a fixedtoothed engagement between the teeth of the coupling area of thecoupling element which is active in the relevant adjusting direction andof the drive wheel when the drive lever is moved out from the zero pointposition and on the other it is guaranteed that the drive lever is resetinto the zero point position without any ratchet noises.

A secondary force acts on the coupling element during an adjustingprocess to produce a torque in the direction of a reinforced coupling ofthe loaded coupling area and drive wheel when the drive lever is movedout of the zero point position. Likewise, a secondary force produces atorque in the direction of lifting the loaded coupling area from thedrive wheel during movement of the drive lever in the direction of thezero point position. This secondary force is preferably achieved throughaxial tensioning of the coupling element, preferably outside of the zeropoint position of the drive lever.

This design ensures, in addition to a quasi play-free drive, a fixedcoupling between the coupling element and drive wheel as well as theelimination of ratchet noises, that the coupling element in the zeropoint position is coupled with the drive wheel through the action of thespring acting on the coupling element and that the coupling element isfixed and thus no rattling or ratchet noises can occur.

Producing the axial tensioning of the coupling element is preferablycarried out through at least one axially acting friction element whichis mounted on the coupling element underneath the active line of therotary point of the coupling element with the connection of the couplingareas to the drive wheel, is supported on a locally fixed part of thedrive and in the zero point position of the drive lever is inactive sothat the coupling areas are coupled to the drive wheel through thespring elastic connection of the coupling element with the drive lever.

Optionally two friction elements can be mounted on the coupling elementone either side next to the drive lever and/or one friction element canbe mounted centrally on the coupling element which engages through anopening in the drive lever.

The or each friction element is preferably formed as a leaf spring.

BRIEF DESCRIPTION OF THE DRAWINGS

The idea on which the invention is based will now be explained withreference to the embodiments shown in the drawings in which:

FIG. 1 is a plan view of an adjustment drive with a coupling elementmounted on the drive lever;

FIG. 2 shows an adjustment drive with an externally toothed drive wheel;

FIG. 3 shows an adjustment drive in the zero point position with aspring supported on the drive axle;

FIG. 4 shows an adjustment drive according to FIG. 3 in a slightlyrotated position wherein the non-loaded coupling area is just liftedfrom the drive wheel;

FIG. 5 shows an adjustment drive according to FIG. 3 in a sectionalview;

FIG. 6 shows an adjustment drive with springs fixed on the housing forthe silent resetting of the coupling element back into the zero pointposition;

FIG. 7 shows an adjustment drive with a spring between the couplingelement and the guide element mounted on the drive lever;

FIG. 8 shows an adjustment drive with friction elements mounted at theside of the drive lever on the coupling element;

FIG. 9 shows an adjustment drive with a friction element mountedcentrally on the coupling element and engaging through an opening in thedrive lever.

DETAILED DESCRIPTION

FIG. 1 shows an adjustment drive with a housing secured against rotationwhere a drive lever 10 or component part 10 connectable to the drivelever is mounted rotatable on an axle 20. A recess 11 is punched out inthe drive lever 10, which is shown shortened here, and a guide element42 which is radially loaded by a spring 14 is guided in the recess. Theguide element 42 which is here formed as a cylinder pin is moulded ontoa coupling element 40 which is mounted between the housing 1 and drivelever 10.

The spring 14 presses the guide element 42 radially outwards from theaxle 20 whereby the coupling element 40 is removed from the axle 20 atthe same time. In this embodiment the spring is formed as a compressionspring 14, but other types of springs, for example leaf or tensilesprings as well as other spring elements such as rubber springs arefundamentally possible.

The radially displaceable coupling element 40 has two coupling areas 41a and 41 b which are formed as teeth and which engage in correspondinginternal teeth 31 of a drive wheel 30. The drive wheel 30 is locatedsubstantially in a plane with the coupling element 40 and is connectedrotationally secured to a gear element (not shown) which is in activeconnection with further gear elements or steps of the adjusting device.

In the illustration of FIG. 1 the drive lever 10 is located in its zeropoint position and the spring 14 presses the coupling element 40radially outwards so that both coupling areas 41 a, 41 b are in positiveengagement with the internal teeth 31 in the toothed sections 44 a, 44b. The radial mobility of the coupling element 40 is thereby notrestricted by the dimensions of the recess 11 in the drive lever 10 sothat a complete engagement of the teeth is possible in the direction ofthe drive wheel 30. The recess 11 is dimensioned in the direction of theaxle 20 so that when the guide element 42 stops against same the twocoupling areas 41 a, 41 b are brought straight out of engagement withthe internal teeth 31.

When the drive lever 10 is operated in the direction of the arrow A aforce acting in the direction of arrow A is exerted through the guideelement 42 on the coupling element 40. This force acts on the couplingarea 41 b which is supported on the corresponding toothed section 44 bof the internal teeth 31 of the drive wheel 30 and turns the drive wheel30 about the axle 20. At the same time the coupling area 41 a is liftedfrom the internal teeth 31 through a sliding block guide (not shown) sothat the guide element 42 is moved in the recess 11 in the direction ofthe axle 20. During resetting of the drive lever 10 into the zero pointposition the coupling area 41 b slides over the internal teeth and thecoupling area 41 a is held by the corresponding slide block guide out ofengagement with the internal teeth 31 until the starting positionillustrated in FIG. 1 is occupied again.

Through the pressing of the coupling element 40 through the spring 14 inthe zero point position both coupling areas 41 a, 41 b are in engagementwith the internal teeth 31 so that no idling path has to be covered upto the engagement of the teeth. The spring 14 furthermore has the effectthat despite a movement of the drive lever 10 without actual adjustmentof the drive wheel 30, the user does not have the feel of an idling pathsince when operating the drive lever 10 he is working against theresistance of the spring 14.

A corresponding sliding block guide fixed on the housing and in whichguide elements are guided so that the coupling areas 41 a, 41 b duringresetting movement of the drive lever 10 into the zero point position donot engage with the internal teeth 31, is not shown in FIG. 1 forreasons of clarity. The principle of the sliding block guide will beexplained with reference to the following figures.

FIG. 2 shows an adjustment drive whose drive lever 10 is likewisemounted rotatable about an axle 20 and has a guide element 43 which ismounted in a radially extending recess 12 of the coupling element 40′.The drive wheel 30 is provided with external teeth 31′ into which thecorresponding coupling areas 41 a, 41 b of the coupling element 40′engage. A spring 15 is attached between the coupling element 40′ and theguide element 43 mounted on the drive lever 10 and loads the couplingelement 40′ in the direction of the drive wheel 30 so that the twocoupling areas 41 a, 41 b engage with the external teeth 31′ in thestarting position.

Two guide elements 51 a, 51 b are fixed on the coupling element 40′ andare each guided in a sliding block guide 5 a, 5 b having sliding blockguide areas 50 a, 53 aand 50 b, 53 b. Likewise a spring element 60 a and60 b is associated with each guide element 51 a, 51 b wherein in theillustrated design the spring elements 60 a, 60 b are formed as aone-piece leaf spring. The spring elements 60 a, 60 b act against thespring 15, that is they press the area of the coupling element 40′ whichis unloaded when the drive lever 10 is returned, away from the externalteeth 31′. However the spring elements 60 a, 60 b are designed andarranged so that in the zero point position of the drive lever 10 noforce is exerted on the guide elements 51 a, 51 b, or the force is lessthan that of the spring 15 so that the coupling element 40′ in the zeropoint position adjoins the external teeth 31′. On the other hand theforce which is exerted on the guide elements 51 a, 51 b outside of thezero point position by the springs 60 a, 60 b is greater than the forceemanating from the spring 15 so that the coupling area 41 a, 41 b whichis unloaded at the time is lifted.

If the drive lever 10 is operated in the direction of the arrow A then aforce is exerted through the guide element 43 on the coupling element40′. The transition area between the sliding block guide areas 50 a, 53a and 50 b, 53 b cause the coupling element 40′ to tilt about thecoupling area 41 b so that the coupling element 40 is moved outwardsagainst the force of the spring 15 along the recess 12 whereby thecoupling area 41 b remains engaged with the external teeth 31′. At thesame time the drive wheel 30 is driven correspondingly through therotational movement of the coupling element 40 about the axle 20 and theguide element 51 b is moved in the sliding block 5 b spaced from thecontour of the sliding block guide area 50 b. The spring element 60 b isthereby pressed radially inwards through the force exerted on the drivelever 10.

As soon as no more force is introduced through the drive lever 10 in thedirection of arrow A the spring element 60 b presses the guide element51 b radially outwards. The free space over the sliding block guide area50 b enables the coupling area 41 b to be lifted from the external teeth31′. Through the force of the spring element 60 b the coupling element40′ is turned about the guide element 51 a which is located on the area53 a until the recess 12 stops the guide element 43. During theresetting movement of the drive lever the two coupling areas 41 a, 41 bare therefore not in engagement with the external teeth 31′, namely thecoupling area 41 b as a result of the spring force of the spring element60 b and the coupling area 41 a as a result of the sliding block guidearea 53 a which is spaced from the external teeth 31′. The resettingmovement therefore takes place without any ratchet noise.

If the drive lever 10 is located in its zero point position then thespring 15 presses the coupling element 40′ back in the direction of theaxle 20 and brings the coupling areas 41 a, 41 b into engagement withthe external teeth 31′.

FIG. 3 shows an adjustment drive with an internally toothed drive wheel30 wherein each one sliding block guide 5 a, 5 b fixed on the housing isin engagement with the guide elements 51 a, 51 b mounted on the couplingelement 40 analogous with FIG. 2. The spring 13 which is mounted here onthe axle 20 of the drive presses the coupling element 40 radiallyoutwards in the direction of the internal teeth 31 of the drive wheel30. The spring 13 thus acts corresponding to the spring 11 in FIG. 1.Movement of the drive lever (not shown) counter-clockwise engenders acorresponding movement of the coupling element 40 and of the drive wheel30, as shown in FIG. 4.

The coupling element 40 is thereby turned slightly about the axle 20 andthe guide element 51 a has been displaced along the shoulder between thesliding block guide area 50 a and the sliding block guide area 53 a. Thecoupling area 41 a has just been lifted from the internal teeth 31 ofthe drive wheel 30 against the externally acting force of the spring 13as a result of the geometric dimensions of the sliding block guide 5 a.The coupling area 41 b is thereby in engagement with the internal teeth31 and drives the drive wheel 30.

The coupling element 40 has a guide element 42 which corresponding tothe arrangement in FIG. 1 is guided in a recess (not shown) throughwhich the rotational movement about the coupling area 41 a isrestricted.

When resetting the drive lever into the zero point position the couplingarea 41 b remains in engagement with the internal teeth 31. Sincehowever the force through the spring still only presses the couplingelement 40 radially outwards the coupling area 41 b slides along on theinternal teeth 31 so that ratchet noise is produced. The coupling area41 a which is relaxed during adjustment remains as a result of thesliding block guide 5 a out of engagement with the internal teeth 31.Only when or shortly before reaching the zero point position does theguide element 51 a move from the area 53 a towards the internal teeth 31and come into engagement with same.

It is obviously possible to make the guide elements 51 a, 51 b fixedrelative to the housing and to provide a sliding block guide on thecoupling element 40.

FIG. 5 shows a sectional view of FIG. 3 in which the arrangement of thedrive lever 10 above the spring 13 and the coupling element 40 can beseen. The recess 11 is stamped or milled in the drive lever 10 wherebythe guide element 42 which is formed integral with the coupling element40 is guided in the recess. The recess 11 causes in interaction with thespring 13 a radially outwardly directed movement of the coupling element40 and thus causes the coupling areas to adjoin the internal teeth 31 inthe zero point position.

One variation of the invention in which there is likewise no ratchetnoise when the drive lever 10 is reset is shown in FIG. 6. The workprinciple thereby corresponds to that of the drive illustrated in FIG.2, where the reference numerals correspond to those of FIG. 2 and therelevant elements have the same function as described in connection withFIG. 2. As opposed to the drive according to FIG. 2 here according toFIG. 6 the coupling element 40 is located as with the drive according toFIG. 1 inside the drive wheel 30. Guide elements 51 a, 51 b are formedon the coupling element 40 and engage in a sliding block guide 5 a, 5 b.

In FIG. 7 the coupling element 40 has a recess 12 and the spring 15 ismounted on the guide element 43 which is formed on the drive lever.Guide elements 51 a and 51 b have corner sections 52 a and 52 b. Thespring 15 causes a constant abutment of the coupling element 40 againstthe internal teeth 31 if the coupling element 40 is located in the zeropoint position. A displacement out of the zero point position leads to acoupling area 41 a, 41 b lifting away from the internal teeth 31. Duringresetting into the zero point position the coupling area 41 a, 41 bwhich is loaded during the adjustment slides along on the internal teeth31 until the starting position shown in FIG. 7 is reached.

FIG. 8 shows a plan view of an adjustment drive which corresponds to theadjustment device according to FIG. 1 where the same reference numeralsdesignate the same function elements of the adjustment drive accordingto FIG. 1.

Differently from the design of the adjustment drive according to FIG. 1,in the adjustment drive illustrated in FIG. 8 however both couplingareas 41 a, 41 b of the coupling element 40 are provided with frictionelements 45 a, 45 b which are arranged on either side of the drive lever10. The friction elements 45 a, 45 b can be fixed on the coupling areas41 a, 41 b or are formed integral on the coupling area 41 a, 41 b andare located underneath the active line of the guide element 42 formingthe rotational point of the coupling element 40 and of the toothedengagement of the toothed sections 44 a, 44 b of the coupling areas 41a, 41 b with the internal teeth 31 of the drive wheel 30 so that a leverarm H is formed which during movement of the drive lever 10 out from thezero point position or during movement of the drive lever 10 into thezero point position cause a corresponding torque which acts on therelevant coupling area 41 a, 41 b of the coupling element 40.

The friction elements 45 a, 45 b are supported on a locally fixed partof the adjustment drive, for example on the housing of the adjustmentdrive so that an axial tensioning of the coupling element 40 is causedand during movement of the drive lever 10 out from the zero pointposition causes a torque on the active side of the coupling element 40,that is on the side which corresponds to the direction of rotation ofthe drive lever 10, in the direction of a toothed engagement of therelevant coupling area 41 a or 41 b with the internal teeth 31 of thedrive wheel 30, whilst during resetting of the drive lever 10 into thezero point position torque arises on this coupling area 41 a, 41 b orthe toothed section 44 a, 44 b associated therewith in the direction oflifting the relevant toothed section 44 a, 44 b out of the internalteeth 31 of the drive wheel 30.

During movement of the drive lever 10 in the direction of arrow A,through the action of the axially tensioned friction element 45 b thetoothed section 44 b of the coupling area 41 b is pressed into theinternal teeth 31 of the drive wheel 30 whilst during resetting of thedrive lever 10 into the zero point position against the direction ofarrow A the torque caused by the friction element 45 b leads to thetoothed section 44 b lifting out from the internal teeth 31 of the drivewheel 30. The toothed section 44 a is lifted out from the internal teeth31 of the drive wheel 30 during the movement of the drive lever 10described above in the direction of the arrow A out from the zero pointposition or during the movement of the drive lever 10 in the directionof the zero point position analogous with the explanation on theadjustment drive according to FIG. 1.

In the zero point position of the drive lever 10 the friction elements45 a, 45 b are inactive, that is they are not axially tensioned and thespring 14 can press the coupling element 40 radially outwards and thusin the zero point position of the drive lever 10 both coupling areas 41a and 41 b of the coupling element 40 are in engagement with theinternal teeth 31 of the drive wheel 30.

The arrangement of the friction elements 45 a, 45 b causes on the onehand a play-free adjustment drive which during resetting of the drivelever 10 into the zero point position causes no ratchet noises to ariseand on the other a fixing of the coupling element 40 so that no rattlingor ratchet noises can arise as a result of the required axial play.

The friction elements 45 a, 45 b are preferably formed as leaf springswhich are supported on one side on the coupling areas 41 a and 41 b andon the other for example on the housing of the adjustment drive.

FIG. 9 shows an alternative to the arrangement according to FIG. 8 witha friction element 46 attached centrally on the coupling element 40′ andwhich engages through an opening 16 in the drive lever 10 and islikewise supported on a locally fixed part of the adjustment drive,preferably on the housing of the adjustment drive.

The action of this one central friction element 46 corresponds to theaction of the two friction elements 45 a, 45 b mounted on the couplingelement 40 at the sides of the drive lever 10, according to FIG. 8, andis likewise mounted underneath the active line of the rotational pointof the coupling element 40 formed by the guide element 42, and thetoothed engagement of the toothed sections 44 a, 44 b of the couplingareas 41 a, 41 b with the internal teeth 31. The distance H′ between thefriction element 46 and the guide element 42 which (distance) is greaterin this embodiment compared with the embodiment of FIG. 8, forms thelever arm for the torque for lifting the coupling area 41 a or 41 b toreinforce the toothed engagement of each active coupling area 41 a, 41 bor for lifting the relevant toothed area 44 a, 44 b out from theinternal teeth 31 during the return of the lever arm 10 into the zeropoint position.

As a further alternative a combination of the embodiments according toFIGS. 8 and 9 is possible, that is the arrangement of three frictionelements 45 a, 45 b and 46, of which two friction elements connected tothe coupling element 40 are arranged at the side of the drive lever 10,whilst a central friction element is provided corresponding to thefriction element 46 according to FIG. 9 on the coupling element 40. Allthe friction elements 45 a, 45 b, 46 are axially tensioned outside ofthe zero point position of the drive lever 10, whilst in the zero pointposition the friction elements 45 a, 45 b and 46 are inactive so thatthe spring 14 presses the guide element 42 outwards, that is pressesboth toothed sections 44 a, 44 b of the coupling areas 41, 41 b into theinternal teeth 31 of the drive wheel 30.

Also the central friction element 46 according to FIG. 9 consistspreferably of a leaf spring which is fixed on the coupling element 40,engages through the opening 16 of the drive lever 10 and is supported ona locally fixed element of the adjustment drive.

What is claimed is:
 1. A drive acting on both sides for an adjustmentdevice, comprising: a swivel mounted drive lever for producing a rotarymovement which starting from a zero point position of the drive levercan take place selectively into a first rotary direction and into asecond opposite rotary direction; a drive wheel which is rotated duringmovement of the drive lever out from the zero point positions; at leastone coupling element mounted on the drive lever and having two couplingareas for transferring torque to the drive wheel; and a sliding blockguide with sliding block guide areas for controlling the at least onecoupling element, wherein the at least one coupling element is mountedradially displaceable and able to tilt in a coupling element guide andis coupled spring elastically with the drive wheel through the twocoupling areas in the zero point position of the drive lever so thatduring movement of the drive lever out from the zero point position atleast one of the coupling areas is non-loaded and is uncoupled from thedrive wheel through the sliding block guide and during movement of thedrive lever in the direction of the zero point position remainsuncoupled.
 2. The drive according to claim 1 wherein the at least onecoupling element is connected to a guide element which engages in aradially extending recess of the drive lever.
 3. The drive according toclaim 1 wherein the drive lever is connected to a guide element whichengages in a radially extending recess of the at least one couplingelement.
 4. The drive according to claim 2 or 3 wherein the guideelement is connected to the radially extending recess through a slideblock.
 5. The drive according to claim 2 wherein the recess is measuredso that the at least one coupling element is movable radially so farthat the two coupling areas are not coupled to the drive wheel.
 6. Thedrive according to claim 1 wherein a spring is mounted between a housingand the at least one coupling element.
 7. The drive according to claim 1wherein a spring is mounted between the drive lever and the at least onecoupling element.
 8. The drive according to claim 7 wherein the springis mounted between the drive lever and a guide element.
 9. The driveaccording to claim 7 wherein the spring is mounted between a guideelement and the at least one coupling element.
 10. The drive accordingto claim 1 wherein the coupling areas of the at least one couplingelement are formed as teeth associated with a corresponding toothing onthe circumference of the drive wheel.
 11. The drive according to claim10 wherein the teeth of the drive wheel are formed as one of the groupof internal teeth and external teeth.
 12. The drive according to claim 1wherein the coupling areas of the at least one coupling element and acircumference of the drive wheel are designed so that the transfer oftorque between the at least one coupling element and the drive wheeltakes place with friction engagement.
 13. The drive according to claim 1wherein the sliding block guide is formed in a cover element.
 14. Thedrive according to claim 1 wherein spring areas are arranged on eachside of the drive outside of the sliding block guide areas and exert onthe at least one coupling element a force acting against a lockingdirection, with the force measured so that a coupling area which isloaded when the drive lever moves out from the zero point position isnot lifted from the drive wheel but is lifted during movement towardsthe zero point position.
 15. The drive according to claim 1 wherein onthe at least one coupling element there are guide elements which areguided in the sliding block guide and which outside of the sliding blockguide areas are in contact with spring areas.
 16. The drive according toclaim 15 wherein the guide elements have a non-rounded corner section.17. The drive according to claim 1 wherein the drive is arranged suchthat a secondary force acts on the at least one coupling element duringan adjusting process so that when the drive lever is moved out from thezero point position a torque is produced on a loaded coupling area inthe direction of the drive wheel and when the drive lever is movedtowards the zero point position a torque is produced in the sense oflifting the loaded coupling area away from the drive wheel.
 18. Thedrive according to claim 17 wherein the two coupling areas of the atleast one coupling element are formed as teeth and a toothed area on acircumference of the drive wheel is associated with the teeth, whereinwhen the drive lever is moved out of the zero point position torque isproduced on a loaded coupling area in a direction of a toothedengagement and when the drive lever is moved towards the zero pointposition torque is produced in a direction of separating the toothedengagement.
 19. The drive according to claim 17 wherein the at least onecoupling element is axially tensioned.
 20. The drive according to claim19 wherein the at least one coupling element is tensioned in the axialdirection outside of the zero point position of the drive lever.
 21. Thedrive according to claim 17 wherein at least one axially acting frictionelement is mounted on the at least one coupling element and is inactivein the zero point position of the drive lever so that the two couplingareas are coupled to the drive wheel through the spring-elasticconnection between the at least one coupling element and the drivewheel.
 22. The drive according to claim 21 wherein two friction elementsare mounted on the at least one coupling element at the side of thedrive next to the drive lever.
 23. The drive according to claim 21wherein the at least one axially acting friction element is mountedcentrally on the at least one coupling element.
 24. The drive accordingto claim 23 wherein the at least one axially acting friction elementmounted centrally on the at least one coupling element engages throughan opening in the drive lever.
 25. The drive according to claim 21wherein the at least one axially acting friction element is supported ona locally fixed part of the drive.
 26. The drive according to claim 21wherein the at least one axially acting friction element is mounted onthe at least one coupling element underneath an active line of a rotarypoint of the at least one coupling element with the coupling of the twocoupling areas with the drive wheel.
 27. The drive according to claim 21wherein the at least one axially acting friction element is formed as aleaf spring.